1. Field of the Invention
In general, the present invention relates to an apparatus, system and method for a self-adjusting computer controlled reel assembly. More particularly, the present invention provides a new and improved reel assembly that may maintain a constant tension and constant slippage setting on the umbilical of an offshore reel as the radius to the umbilical varies and the deployment direction is reversed.
2. Description of the Prior Art
When subsea blowout preventer stacks are lowered to the seafloor to facilitate the drilling of oil and gas wells, they are lowered on a drilling riser, which has a long conduit with an inner diameter typically about nineteen inches, which acts as the main conduit for the drilling operations. On the outside of this conduit will be flotation material to make it lighter in water, high pressure circulation lines called choke and kill lines, and control umbilicals. The control umbilicals can be hydraulic, electrical, fiber optic, or a combination of these.
The umbilicals are clamped to the high pressure lines on the riser such that the drilling riser carries the weight of the deployed lines. The umbilicals are handled at the surface by reels, which must payout the umbilical when the drilling riser is lowered and rewind the umbilical when the drilling riser is retrieved. Umbilicals may be hoses, wire rope, cable, hoses, fiber optics, electrical, or combinations of these.
A first level of control of these reels was to have a valve controlling a motor on the reels and simply keep up with the movement of the drilling riser. This was made practical with a “service loop” which sent the umbilicals over a first sheave, down a loose loop, back up over a second sheave, and then clamped to the riser.
A next level of control was to simply use an air throttle and put the umbilical in tension at all times. When the drilling riser is lowered, it pulls the motor against the pneumatic supply and pumps air back into the air system, somewhat like regeneration, or dumped the generated air across a relief valve. Dumping the generated air is more workable as the pneumatic supply is likely of too high a pressure to pump back into. As the radius to the umbilical being deployed from a full spool to an empty spool can vary by as much as 3/1, an umbilical tension of 1,000 lbs. at the outer wrap will translate into 3,000 lbs. at the inner wrap. This means that you must have personnel monitoring the reel to keep the tension down with a reasonable range. Furthermore, you have a slip clutch to prevent high tension if a drilling riser is lowered when the brakes are set on the reel; a slip clutch setting of 1,500 lbs. at the outer wrap becomes a slip clutch setting of 4,500 lbs. at the inner wrap.
What this means is that in all these cases, personnel must be committed to monitor and control the umbilical tension at all times during the running operations. This added head count in a space constrained expensive offshore rig is required at the critical time when the blowout preventer stack and drilling riser is run and personnel commitment is at the maximum.
Even with the added personnel commitment to monitor and control the umbilical tension, no solution has been available for this high safety slippage setting when the umbilical is being paid off from the inner wraps. With the long studies of trying to reduce personnel requirements on these offshore rigs, there has been no solution offered for these problems.
Prior art attempts at improvements to this problem have obviously not provided the desired solutions. Thus, there is a need for an apparatus, process and or system that provides a self-adjusting intelligent reel assembly for reels. The above discussed limitations in the prior art is not exhaustive. The current invention provides an inexpensive, time saving, more reliable apparatus, method and system for reels where the prior art fails.